步骤1：声明属性

@property (nonatomic) NSRange lastRange;

步骤2：在TextView代理中,添加：

- (void) textViewDidChangeSelection:(UITextView *)textView

    NSRange currentRange = NSMakeRange(textView.selectedRange.location,textView.selectedRange.length);

    if (currentRange.length == 0) {
        NSLog(@"Nothing selected");
        _lastRange = currentRange;
    }
    else {
        if (currentRange.location < _lastRange.location) {
            NSLog(@"Selecting LEFT");
        }
        else {
            NSLog(@"Selecting RIGHT");
        }
    }
}

OSX

OSX具有所需的所有功能,需要更多的工作,但这是我想出了一个工作,一致的解决方案.重命名是可选的,或者…鼓励…

第1步：将NSTextView子类化

在你的SubClass.h中：

#import <Cocoa/Cocoa.h>

@interface TheSelectionizer : NSTextView

@property (nonatomic) NSRange lastAnchorPoint;

@end

在你的SubClass.m

#import "TheSelectionizer.h"

- (void)setSelectedRange:(NSRange)charRange affinity:(NSSelectionAffinity)affinity stillSelecting:(BOOL)stillSelectingFlag {

    if (charRange.length == 0) {
        _lastAnchorPoint = charRange;
    }
    [super setSelectedRange:charRange affinity:affinity stillSelecting:stillSelectingFlag];
}

@end

步骤2：实现NSTextViewDelegate

- (NSRange) textView:(NSTextView *)textView willChangeSelectionFromCharacterRange:(NSRange)oldSelectedCharRange tocharacterRange:(NSRange)newSelectedCharRange {

    if (newSelectedCharRange.length != 0) {

        TheSelectionizer * selectionizer = (TheSelectionizer *)textView;

        int anchorStart = (int)selectionizer.lastAnchorPoint.location;
        int selectionStart = (int)newSelectedCharRange.location;
        int selectionLength = (int)newSelectedCharRange.length;

        /*
         If mouse selects left,and then a user arrows right,or the opposite,anchor point flips.
         */
        int difference = anchorStart - selectionStart;
        if (difference > 0 && difference != selectionLength) {
            if (oldSelectedCharRange.location == newSelectedCharRange.location) {
                // We were selecting left via mouse,but now we are selecting to the right via arrows
                anchorStart = selectionStart;
            }
            else {
                // We were selecting right via mouse,but now we are selecting to the left via arrows
                anchorStart = selectionStart + selectionLength;
            }
            selectionizer.lastAnchorPoint = NSMakeRange(anchorStart,0);
        }

        // Evaluate Selection Direction
        if (anchorStart == selectionStart) {
            if (oldSelectedCharRange.length < newSelectedCharRange.length) {
                // Bigger
                NSLog(@"Will select right in overall right selection");
            }
            else {
                // Smaller
                NSLog(@"Will select left in overall right selection");
            }
        }
        else {
            if (oldSelectedCharRange.length < newSelectedCharRange.length) {
                // Bigger
                NSLog(@"Will select left in overall left selection");
            }
            else {
                // Smaller
                NSLog(@"Will select right in overall left selection");
            }
        }
    }

    return newSelectedCharRange;
}

我发布了一个项目,以防有人想尝试或想要看到它.

完整的“项目”可用HERE